Extensibility

Any source format for micro-history data must be extensible
in order to accommodate unforeseen circumstances or cultural variations.

There are three main types of extension considered here:
Extensions to the schema itself to define new element types, extended
properties for Person, Animal, Place, Group, or Event entities, and extended
vocabularies for types, etc. The latter two are deliberately made easy since
they will be more common. Extending the core schema is controversial, and not
really recommended, but the possibility is included here for completeness.

Note that there is no real need to introduce other types of
Person-to-Person linkage to supplement the existing ones that represent biological
lineage and association via Role and Relationship through shared Events. The
fact that narrative text can reference any Person, Animal, Place, Group, or
Event means that the data model already has a fundamental capability to link elements
for arbitrary reasons. This, in turn, is necessary for it to be applicable to
micro-history in general. Although the conclusional sub-model, in the form of
Properties, describes relationships in terms of a normalised vocabulary, the
informational sub-model, in the form of the Source entity, can describe any
subject-to-subject relationship using the informal vocabulary of the user or
the source.